x or j heads

[wayne & tina]

Can anyone tell me the difference between x-heads and j-heads for a 340.
And years they were produced. Which ones are better? Thanks, Wayne

[mopa...@home.com]

X heads are the original 340 heads made in 1968. They have 202/160
valves. They were used from 1968 to 1970.

J heads were made from 1972-1973. They are basically 360 heads. Smaller
ports than the X heads and smaller valves too (188/160). They also have
hardened seats for unleaded gas.

Which is best? that depends on the reason why you need the heads. If
they are for a restoration and the car was made before 1971 then the X
heads are needed. If you are racing the 340 or other small blocks then
the X heads will make more power. If the car is to be used on the street
with pump gas and good driveability then go with the J heads.

Also not many of you may know that there is one more regular 340 head
out there. That is the O head, made in 1971. It is rather rare but it is
basically a large valve version of the J head.

And for those who like very obscure parts there is the TA head aswell.
It is also a 360 head with offset pushrod holes for serious porting
work.

hope this helps

[Joshua S.]

I have to disagree. The J heads have the same port size as X
heads.

Joshua Skinner

[mopa...@home.com]

I have a pair of X heads in my garage and a pair of 360 heads (1975) and
the ports are slightly different. Also the TA head was 1970 only and it
is a 360 head. i have pictures of one and it clearly shows the AAWJ360
stamping. The real identifier are the offset pushrod holes.

Keith Mezzina wrote:
>
> I was about to say the same thing. I was also under the idea that the
> X heads *were* the TA Heads. The only difference with the TA head is
> the offset pushrod holes.

>
> On Mon, 05 Oct 1998 22:10:49 -0700, "Joshua S."
> <Dartman@\"deletethis\"uswest.net> wrote:
>
> >I have to disagree. The J heads have the same port size as X
> >heads.
> >
> >Joshua Skinner
> >
> >mopa...@home.com wrote:
> >>
> >> X heads are the original 340 heads made in 1968. They have 202/160
> >> valves. They were used from 1968 to 1970.
> >>
> >> J heads were made from 1972-1973. They are basically 360 heads. Smaller
> >> ports than the X heads and smaller valves too (188/160). They also have
> >> hardened seats for unleaded gas.
>

> -----------------------------------------------------
> Don't look back, they might be gaining on you.
> Don't take life too seriously, you won't get out alive.
> Friends help you move; Real friends help you move bodies.
> I have seen the evidence. I want DIFFERENT evidence!

[mopa...@home.com]

the casting number for the TA head is 3418915. The casting number for
the X head is 2531894. The casting number for J heads are 3418915 in
1972 and for 1973 the number is 3671587. This is stamped on the heads so
rough indentification is possible.

[Joshua S.]

The TA heads were different, but the only difference is the
relocated pushrod hole to allow more extensive porting.

Joshua

[Buddy Ward]

The T/A heads were usually U or O's, but not X's .
They were, of course 2.02 valved heads.

Greg

[Sjkk143]

What location is the castinng stamp at.

[moparman]

the casting numbers are two of the intake ports near the spring seat.
There will be two stampings on the head. One will go aawj360 (or aawj340
depending on the head) the other is will be the 7 digit number that
identifies the cylinder head family.